Despite it is commonly known that “smoking is harmful to your health”, the number of smokers worldwide is up to 1 billion, and the number is increasing every year. According to the statistical data from the World Health Organization, about 4.9 million people die of diseases caused by smoking each year. Although smoking may cause serious respiratory diseases and cancer, it remains extremely difficult for smokers to quit smoking completely.
The active ingredient in a cigarette is nicotine. During smoking, nicotine, along with a lot of tar aerosol droplets produced in the burning cigarette, enters smoker's alveolus and is rapidly absorbed. After being absorbed into the blood of a smoker, nicotine then produces an effect on the receptors of the smoker's central nervous system, which makes him/her relax and enjoy an inebriety similar to that produced by an exhilarant.
Nicotine is a kind of alkaloid with low molecular weight. A small dose of nicotine is essentially harmless to human body and its half-life in blood is quite short. The major harmful substance in tobacco is tar, and the tar in tobacco is composed of thousands of ingredients, tens of which are cancerogenic substances. At present, it has been proven that passive smoking can be more harmful on non-smokers.
Some cigarette substitutes that contain only nicotine without tar have been proposed, and many of them, such as “nicotine patch”, “nicotine mouthwash”, “nicotine chewing gum”, “nicotine drink” etc., are made of pure nicotine. Although these cigarette substitutes are free from tar, their major disadvantage is that an effective peak concentration cannot be reached in the blood of a smoker due to slow absorption of nicotine. In addition, these cigarette substitutes cannot satisfy habitual smoking actions of a smoker, for example, inhaling action or sucking action, and thus are not likely to be widely accepted as effective substitutes for quitting smoking.